Radiotherapy is known which cures a patient by irradiating an affected part (a tumor) with therapeutic radiation. It is desired for the radiotherapy to reduce a dose of the therapeutic radiation radiated to normal cells different from the affected part. As the radiotherapy for curing the affected part (a pulmonary tumor is exemplified) that is moved synchronously with a physiological motion such as a respiration and a heartbeat, a moving body tracking irradiation and a respiration synchronization irradiation (gated irradiation) are applied. The moving body tracking irradiation is a method of changing a radiation direction or radiation field of the therapeutic radiation based on a position of the affected part. The gated irradiation is a method of radiating the therapeutic radiation or stopping the therapeutic radiation based on the position of the affected part. The moving body tracking irradiation and the gated irradiation are preferably such that the dose of the therapeutic radiation radiated to the normal cells different from the affected part is smaller, as compared with an irradiation of an area having a range wider than the area of the affected part. For the moving body tracking irradiation and the gated irradiation, it is desired to measure the position of the affected part more accurately at a higher speed.
Japanese Laid-Open Patent Application (JP-P 2004-136021A) discloses a concentrated irradiation radiotherapy apparatus for creating an image whose artifact caused by scattered rays is little, in parallel to the therapy. The concentrated irradiation radiotherapy apparatus is characterized by including: a first radiation source; a second radiation source; a radiation detector located oppose to the first radiation source with an subject therebetween; a moving mechanism for moving the first and second radiation sources together with the radiation detector to the subject; a first high voltage generator for supplying an electric power to the first radiation source in order to generate radiation for a data collection with a relatively low dose from the first radiation source; a second high voltage generator for supplying an electric power to the second radiation source in order to generate therapeutic radiation with a relatively high dose from the second radiation source; a controller for controlling the second high voltage generator in order to generate the therapeutic radiation from the second radiation source and controlling the first high voltage generator in order to generate the radiation for the data collection from the first radiation source; a compensator for compensating data outputted from the radiation detector correspondingly to a period while the radiation for the data collection is generated from the first radiation source, based on the data outputted from the radiation detector correspondingly to a period while the generation of the radiation for the data collection from the first radiation source is stopped; an image reconfiguring unit for instantly reconfiguring an image data, based on the compensated data; and a display for displaying an mage based on the image data.
Japanese Patent JP3746747B discloses a radiotherapy apparatus that can monitor a state of a therapy field at real time, even during the radiotherapy with radiation. The radiotherapy apparatus includes: a radiation irradiating head for irradiating the therapy field of an subject with the therapeutic radiation; an O-type gantry to which the radiation irradiating head is movably attached; an X-ray source for irradiating the therapy field of the subject with diagnosis X-rays; a sensor array for detecting transmission X-rays of the diagnosis X-rays transmitted through the subject and outputting as a diagnosis image data; an image processor for creating a diagnosis image of the therapy field, based on the diagnosis image data; and a controller. The radiation irradiating head is movably connected to the O-type gantry and includes ahead swinging mechanism for swinging the radiation irradiating head so that the therapy radiation radiated by the radiation irradiating head follows the motion of the therapy field. The controller controls a position of the head swinging mechanism so that the irradiation field of the radiation irradiating head follows the therapy field, based on the diagnosis image, the position of the radiation irradiating head and a swinging state of the radiation irradiating head, and controls irradiation of the radiation irradiating head so that the therapeutic radiation are radiated from the radiation irradiating head, after the positional control of the head swinging mechanism. The sensor array is moved in linkage to the movement of the radiation irradiating head on the O-type gantry.
Japanese Laid-Open Patent Application (JP-P 2006-21046A) discloses a radiotherapy apparatus that can monitor a state of a therapy field at real time, even during the radiotherapy with radiation. The radiotherapy apparatus includes; an O-type gantry; a radiation irradiating head that is movably arranged in the O-type gantry and irradiates the therapy field of an subject with the therapeutic radiation; an X-ray source that is movably arranged in the O-type gantry and irradiates the therapy field of the subject with the diagnosis X-rays; and a sensor array that is movably arranged in the O-type gantry, detects transmission X-rays of the diagnosis X-rays transmitted through the subject, and outputs them as diagnosis image data. The sensor array is arranged at the symmetric position with the radiation irradiating head therebetween and moved in linkage to the movement of the radiation irradiating head on the O-type gantry, and the X-ray source is moved in linkage with the motion of the sensor array.